Planar-type and fin-type semiconductor devices have been studied in order to miniaturize semiconductor devices each including a substrate, such as a silicon substrate. Such semiconductor devices mostly utilize reduction of the short channel effect by using source/drain extension regions (hereinafter simply referred to as extension regions). In order to reduce the short channel effect, shallow extension regions need to be formed, and the extension regions need to be heavily doped with an impurity. For this reason, a technique called plasma doping in which silicon, etc., is doped with an impurity by using plasma started to be developed in the late 1980s (see NON-PATENT DOCUMENT 1). Research and development have been directed at forming shallow extension regions of high impurity concentration using plasma doping since the late 1990s (see NON-PATENT DOCUMENTS 2 and 3).